I'm just old enough to remember slide rules, and doing a little bit of school work with them. I've still got my father's fairly expensive one tucked away in a drawer. My dad was a big convert to calculators, and I remember the first one we had in the house. It cost over $100 back in the late 70's and really didn't do much.
I remember my dad telling me that they were calling some of the scientific calculators "Electronic Sliderules" in order not to scare the engineers too much.
Now, sitting on the desk in front of me is my HP-41CV. The pinnacle of programmable calculators. There's a whole 'nother technology that's come and gone in less than a lifetime. I still use my 41 as a calculator on a daily basis, but I can't remember the last time I programmed it. RPN rules!